Studies on small intestinal transport of peptides will be carried our using isolated brush border membrane vesicles in order to elucidate mechanisms of peptide transport. The brush border membrane vbesicles are devoid of cytoplasmic peptidases, an can be treated with papain to remove oligopeptidases located on the membrane. Studies with papain-treated vesicles will yield valuable information on transport of peptides per se, uncomplicated by the transport of free amino acids resulting from hydrolysis by cytoplasmic and membrane peptidases. Characteristics of peptide transport will be determined using normal and papain-treated vesicles with radioactive peptides. The effect of increased osmolarity in the incubation medium, and of lysis of vesicles in a hypotonic medium on peptide uptake will be studied to estimate the contribution of binding to the membrane in the uptake mechanism. Peptide transport profiles obtained with normal and papain-treated vesicles will be compared in order to evaluate the contribution of free amino acids in the uptake of peptides. The ratios of maximum overshoot values to the equilibrium values will be calculated to estimate the extent of active transport of peptides and will be compared with the ratios for free amino acids. The ionic requirements for peptide transport will be determined by using various cations and a proton gradient. The effects of membrane potential on peptide transport will be measured with various anions and ionophores. Experiments using di, tri and tetra peptides will be conducted to investigate the specificity of peptide transport regarding the maximum size of peptide transported by carrier mechanisms. Competition studies with various peptides will be done in order to determine whether peptides are transported by multiple systems or by a single common uptake system. The effects of various amino acids on uptake of peptides will be investigated to evaluate the independence of peptide uptake systems from amino acid transport. The kinetic characteristics f transport, km and Vmax, will be determined and compared with those for the constituent free amino acids. The above studies on mechanisms of transport of peptides will be of great significance in our understanding of protein nutrition in health and disease.